Brent wheels are great but pricey for new and used. That beind said, and not being sure of what your budget is, I'd recommend a Shimpo Clay Boss or Big Boss - between $300-$700. I have both (Big Boss I got frmo an art center that was going out of business for $200, my Clay Boss (Elite) was a b-day gift from hubby) and both can center 25 lbs with no problem - I've never done 50 but the torque on the wheel would suggest it could. The wheel is very quiet, and has a removable pan. If you can, spend the extra to get the optinoal shelf that is attached. It feels awkward at first, but when I'm at my wheel that doesn't have it, I'm at a loss for space. Good luck!
The old maxim you get what you pay for isn't always true, but for potters wheels I think it is. Shimpo doesn't make the Clay Boss.